The present invention relates to novel liquid crystal polymer blends for use in medical devices.
Catheter devices having a dilatation balloon mounted at the distal end of the catheter are useful in a variety of medical procedures. A balloon reservoir may be used to deliver a biologically compatible fluid, such as radiologically opaque fluid for contrast x-rays, to a site within the body. Radial expansion of a balloon may be used to expand or inflate a stent positioned within the body. A balloon may also be used to widen a vessel into which the catheter is inserted by dilating the blocked vessel. For example, in the technique of balloon angioplasty, a catheter is inserted for long distances into blood vessels of extremely reduced diameter and used to release or dilate stenoses therein by balloon inflation. These applications require thin walled high strength relatively inelastic balloons of accurately predictable inflation properties.
Depending on the intended use of the balloon and the size of the vessel into which the catheter is inserted, the requirements for strength and the size of the balloon vary widely. Balloon angioplasty has perhaps the most demanding requirements for such balloons. Typically, this application requires that the balloons have uniformly thin walls and a small diameter in their unexpanded state. The walls and waist thicknesses of the balloon limit the minimum diameter of the catheter distal end, and therefore determine the limits on minimum blood vessel diameter treatable by this method, as well as the ease of passage of the catheter through the vascular system.
Further requirements include high balloon strength which enables the balloon to push open a stenosis and to avoid bursting of the balloon under the high internal pressures necessary to inflate the balloon at the site of the stenosis. The balloon must also be sufficiently elastic to allow a surgeon to vary the diameter of the balloon as required to treat individual lesions. However, the balloon must have relatively low elasticity in order to accurately control the balloon diameter, and variations in pressure must not cause wide variations in balloon diameter.
These physical requirements may conflict with one another and thus can make the formation of a balloon from a single material difficult depending on the end use of the balloon. Various approaches have been taken including melt blending materials and the use of multilayer balloon structures.
Blends of liquid crystal polymers and thermoplastic non-LCP base polymers have been employed including polyesteramide and polyester-type LCPs, for example. See commonly assigned U.S. Pat. No. 6,242,063 and U.S. Pat. No. 6,284,333.
The present invention relates to the use of melt blending novel polyesterimide anhydride liquid crystal polymers (LCP-PA) with various other polymeric materials for use in catheter devices.
The polyesterimide anhydride liquid crystal polymers have terminal and/or lateral anhydride groups.
In some embodiments, the LCA-PA is melt blended with a polyester, a polyamide, a copolymer thereof or a mixture thereof. The mixture is suitable for use in making extruded tubular structures for use in portions of medical devices such as catheter shafts, dilatation balloons, and so forth.